Description:

dhcpcd -U [interface] or dhcpcd --dumplease [interface] is useful to dump the current lease information.
I use this command to dump some information like dhcp6_pd_prefix for other network configure scripts.

However, this command crashes with SIGSYS on the Arch Linux. This made this command entirely not operational.

After recompiling the dhcpcd 9.4.1-1 with options=('!strip'), I got the stack trace[1] and found out the reason is the lack of newfstatat(2) in its seccomp rule.
And it seems like upstream has made a patch[2] that fixes this issue, but the patch has not been merged.

[1] Attached file dhcpcd-U-stacktrace.txt. Note the si_signo=31 and _syscall=262 in the $_siginfo.
[2] https://github.com/NetworkConfiguration/dhcpcd/commit/b4d8a349e55d269866bc6ee6e3bb3b03ef293eda

It seems like this problem only occurs with the recent version of glibc, so this issue doesn't appear on other distros such as Ubuntu.
So maybe we can apply this patch in the downstream package now, before the upstream finally got this patch merged and release a new version of dhcpcd.

Additional info:
* package version(s): dhcpcd 9.4.1-1
* config and/or log files etc: see links above.
* link to upstream bug report: nope, the upstream fixed this issue by chance when they tried to fix another issue[3].

[3] https://github.com/NetworkConfiguration/dhcpcd/issues/99#issuecomment-1126793972

Steps to reproduce:
1. Obtain a lease with dhcpcd: dhcpcd -w eth0
2. Dump lease information: dhcpcd -U eth0
And then you will see
root@archlinux:~ # dhcpcd -U ppp0
Bad system call (core dumped)